Acetyl salicylic acid.



UNIT D STATES PATENT QFFICE.

FELIX IIOFFMANN, OF ELBERFELD, GERMANY, ASSIGNOR TO THE FARIiEN-FABRIKEN OF ELBERFELD COMPANY, OF NEW YORK.

ACETYL SALICYLIC ACID.

SPECIFICATION forming part of Letters Patent No. 644,077, dated February27, 1900. Application filed August 1, 1898 Serial No. 687,385.(Specimens) T etZZ whom it may concern:

Be it known that I, FELIX HOFFMANN, doctor of philosophy, chemist,(assignor to the FARBENFABRIKEN on ELBERFELD COMPAN r, of New York,)residing at Elberfeld, Germany, have invented a new and usefulImprovement in the Manufacture or Production of Acetyl Salicylic Acid;and I hereby declare the following to be a clear and exact descriptionof my invention.

In the Amzalcn der Chemie und Pha-rmacie, Vol. 150,-pages 11 and 12,Kraut has described that he obtained by the action of acetyl chlorid onsalicylic acid a body which he thought to be acetyl salicylic acid. Ihave now found that on heating salicylic acid with acetic anhydride abody is obtained the properties of which are perfectlydiiferent fromthose of the body described by Kraut. According to my researches thebody obtained by means of my new process is undoubtedly the real aeetylsalicylic acid ococn, o .H (J 4\ coon.

Therefore the compound described by Kraut cannot be the real acetylsalicylic acid, but isanothercompound. In thefollowinglpoint outspecifically the principal differences between my new compound and thebody described by Kraut.

If the Kraut product is boiled even for a long while with water,(according to Krauts statement,) acetic acid is not produced,while mynew body when boiled with water is readily split up, acetic andsalicylic acid being produced. The watery solution of the Kraut bodyshows the same behavior on the addition of a small quantity of ferricchlorid asa watery solution of salicylic acid when mixed with a smallquantity of ferric chlorid-that is to say, it assumes a violet color. Onthe contrary, a watery solution of my new body when mixed with ferricchlorid does not assume a violet color. If a melted testportion of theKraut body is allowed to cool, it begins to solidify (according toKrauts statement) at from 118 to 1l8.5 Centigrade, while a melted testportion of my product solidifies at about 70 centigrade. Themelting-points of the two compounds cannot be compared, be-

cause Kraut does not give the melting-point of his compound. It followsfrom these details that the two compounds are absolutely different.

In producing my new compound Ican proceed as follows, (without limitingmyself to the particulars given:) A mixture prepared from fifty parts ofsalicylic acid and seventy- 6o five parts of acetic anhydride is heatedfor about two hours at about 150 centigrade in a vessel provided with areflux condenser. Thus a clear liquid is obtained, from which on coolinga crystalline mass is separated, which is the acetyl salicylic acid. Itis freed from the acetic anhydride by pressing and then recrystallizedfrom dry chloroform. The acid is thus obtained in the shape ofglittering white needles melting at about 135 cen- 7o tigrade, which areeasily soluble in benzene, alcohol, glacial acetic acid, and chloroform,but difiicultly soluble in cold water. It has the formula H 6 coon andexhibits therapeutical properties.

Having now described my invention and in what manner the same is to beperformed, what I claim as new, and desire to secure by Letters Patent,is-

As a new article of manufacture the acetyl salicylic acid having theformula:

coon being when crystallized from drychloroform 9c in the shape of whiteglittering needles, easily soluble in benzene, alcohol and glacialacetic acid, difficultly soluble in cold water, being split by hot waterinto acetic acid and salicylic acid, melting at about 135 centigrade,substantially as hereinbefore described.

In testimony whereof I have signed my name in the presence of twosubscribing witnesses.

FELIX HOFFMANN.

lVitnesses:

R. E. JAHN, OTTO Konre.

